Transmission line structure for transmitting radio signals

ABSTRACT

A transmission line structure for transmitting radio signals includes a first transmission line, a first ground region, and a second transmission line. The first transmission line is arranged on a first layer of a circuit board. The first transmission line includes a first signal line and a second signal line. The first ground region is arranged between the first and second signal lines. The first and second signal lines do not contact the first ground region. The second transmission line is arranged on a second layer of the circuit board, and the second layer is different from the first layer. The second transmission line does not contact the first transmission line, and the second transmission line interleaves with the first signal line, the second signal line and the first ground area.

CROSS REFERENCE TO RELATED APPLICATIONS

This Application claims priority of Taiwan Patent Application No.104108581 filed on Mar. 18, 2015, the entirety of which is incorporatedby reference herein.

BACKGROUND OF THE INVENTION

Field of the Invention

The disclosure generally relates to a transmission line structure, andespecially to a transmission line structure for transmitting radiosignals.

Description of the Related Art

In order to achieve better area utilization, it is often necessary tocross and interleave various kinds of signal lines. For example, thesignal lines could be utilized to transmit many radio signals of a radiofrequency, intermediate frequency, and direct current. In order to avoida short-circuit, which can be caused by interleaving various kinds ofsignal lines, bond-wiring and back-board wiring are utilized to crossand interleave with the signal lines. However, utilizing the bond-wiringincreases costs, and may result in high-frequency effects such asparasitism and coupling, affecting the efficiency of the circuit. Inaddition, although utilizing the back-board wiring does not increase thecost, the back-board wiring results in high-frequency effects,detracting from the circuit's performance. For example, when groovingthe slot and arranging signal lines, the slot will damage the continuityof the ground layer. In addition, wiring between different signal lineswill also cause interference for radio signals. Therefore, atransmission line structure is needed to reduce the high-frequencyeffects without sacrificing circuit performance and increasing the cost.

BRIEF SUMMARY OF THE INVENTION

In order to solve the aforementioned problem, the invention proposes atransmission line structure for transmitting signals which can reducehigh-frequency effects and avoid affecting circuit performance. Thetransmission line structure of the present invention is a multi-linestructure which combines the single-line structure and the coplanarwaveguide. The transmission line structure can convert the up-and-downelectrical field of the transmission line into the left-and-rightelectrical field, and reduce interference with other transmission lines.In addition, by adjusting the line width and spacing of transmissionlines, the resistance-matching could be improved and the radiationeffect could be reduced to avoid deteriorating the circuit performance.

In one aspect of the invention, a transmission line structure fortransmitting radio signals is provided. The transmission line structureincludes a first transmission line, a first ground region and a secondtransmission line. The first transmission line is arranged on a firstlayer of a circuit board. The first transmission line includes a firstsignal line and a second signal line. The first terminal of the firstsignal line connects to the first terminal of the second signal line,and the second terminal of the first signal line relative to the firstterminal connects to the second terminal of the second signal linerelative to the first terminal. The first ground region is arrangedbetween the first and second signal lines. The first and second signallines do not contact the first ground region. The second transmissionline is arranged on a second layer of the circuit board, and the secondlayer is different from the first layer. The second transmission linedoes not contact the first transmission line, and the secondtransmission line interlaces with the first and second signal lines andthe first ground layer.

In another aspect of the invention, the first signal line and the firstground area are spaced by a first spacing, and the second signal lineand the first ground are spaced by the first spacing. The value of theresistance of the first transmission line is related to the firstspacing and line widths of the first signal line and the second signalline. In addition, the transmission line structure further includes asecond ground area and a third ground area arranged on the first layer,and the first signal line is arranged between the first ground layer andthe second ground layer, the second signal line is arranged between thefirst ground layer and the third ground layer, the first signal line andthe second ground area are spaced by a second spacing, and the secondsignal line and the third ground area are spaced by a third spacing. Thefirst spacing is equal to the second spacing and the third spacing. Theresistance value of the first transmission line is related to the firstspacing, the second spacing, the third spacing, and line widths of thefirst signal line and the second signal line.

In another embodiment, the width of the first ground area is larger thanor equal to three times the line widths of the first signal line and thesecond signal line. The width of a portion of the second ground areawhich is adjacent to the first signal line is larger than or equal tothree times the line width of the first signal line, and the width of aportion of the third ground area which is adjacent to the second signalline is larger than or equal to three times the line width of the secondsignal line. The first transmission line is a coplanar waveguide. Inaddition, the first signal line, the second signal line and the firstground area are vertical to the second transmission line. Lengths of thefirst signal line, the second signal line, and the first ground area arelonger than or equal to the length of the second transmission line.

In another embodiment, the first transmission line further comprises afirst single-line area and a second single-line area, the firstsingle-line area connects the first terminal of the first signal lineand the first terminal of the second signal line, the second single-linearea connects the second terminal of the first signal line and thesecond terminal of the second signal line, and the second transmissionline does not interleave with the first single-line area and the secondsingle-line area. Furthermore, the resistance value of the firstsingle-line area is equal to an equivalent resistance value of the firstsignal line and the second signal line, and the equivalent resistancevalue of the first signal line and the second signal line is equal tothe resistance value of the second single-line area.

In another aspect of the invention, a transmission line structure fortransmitting radio signals is provided. The transmission line structureincludes a first transmission line and a second transmission line. Thefirst transmission line is arranged on a first layer of a circuit board.The first transmission line includes at least three signal lines, andthe transmission line structure includes at least two ground areas. Eachof the at least two ground areas are arranged between every two of theat least three signal lines. The second transmission line is arranged ona second layer of the circuit board, and the second layer is differentfrom the first layer. The second transmission line interleaves with atleast three signal lines and at least two ground areas.

BRIEF DESCRIPTION OF DRAWINGS

The invention can be more fully understood by reading the subsequentdetailed description and examples with references made to theaccompanying drawings, wherein:

FIG. 1A is a top view of a transmission line structure according to anembodiment of the invention;

FIG. 1B is a bottom view of a transmission line structure according toan embodiment of the invention;

FIG. 2 is another top view of a transmission line structure according toan embodiment of the invention.

Corresponding numerals and symbols in the different figures generallyrefer to corresponding parts unless otherwise indicated. The figures aredrawn to clearly illustrate the relevant aspects of the embodiments andare not necessarily drawn to scale.

DETAILED DESCRIPTION OF THE INVENTION

In order to illustrate the purposes, features and advantages of theinvention, the embodiments and figures of the invention are shown indetail as follows. This description is made for the purpose ofillustrating the general principles of the invention and should not betaken in a limiting sense. It should be understood that the embodimentsmay be realized in software, hardware, firmware, or any combinationthereof.

FIG. 1A is a top view of a transmission line structure 10 according toan embodiment of the invention, and FIG. 1B is a bottom view of atransmission line structure 10 according to an embodiment of theinvention. The transmission line structure 10 is utilized to transmit atleast one radio signal, such as radio frequency (RF) signal,intermediate frequency (IF) signal and direct current (DC) signal. Inone embodiment, the transmission line structure 10 includes a firsttransmission line 120, a ground area 130 (the first ground area) and asecond transmission line 162. The first transmission line 120 and thesecond transmission line 162 are utilized to transmit different radiosignals respectively. For example, the first transmission line 120transmits the radio signal, and the second transmission line 162transmits the DC signal. As shown in FIG. 1A, the first transmissionline 120 and the ground area 130 are arranged on the first layer 100A ofa circuit board. As shown in FIG. 1B, the second transmission line 162is arranged on the second layer 100B of the circuit board. Specifically,the slot 160 and the ground area 136 are included in the second layer100B of the circuit board, and the second transmission line 162 isarranged within the slot 160. The second layer 100B is different fromthe first layer 100A, and the first transmission line 120 does not touchthe second transmission line 162 to avoid causing a short-circuit. Forexample, the circuit board is a printed circuit board (PCB), and thefirst layer 100A and the second layer 100B are on the front and the backof the circuit board. In another embodiment, the first layer 100A andthe second layer 100B are both arranged on the front board or the backboard of the circuit board, but they are manufactured by differentmanufacturing conditions or processes. The present invention does notlimit it thereto.

In the embodiment of FIG. 1A, the first transmission line 120 includesthe signal line 122 (the first signal line) and the signal 124 (secondsignal line). The ground area 130 (first ground area) is arrangedbetween the signal lines 122 and 124, and the signal lines 122 and 124do not contact the ground area 130 to avoid causing a short-circuit. Theground area 130 could include at least one via hole 130V forelectrically connecting the ground area of the second layer 100B. Inaddition, the second transmission line 162 is interleaved with thesignal lines 122 and 124 and the ground area 130. For example, thesignal lines 122 and 124 and the ground area 130 are vertical to thesecond transmission line 162 to arrange the wiring on the circuit boardefficiently and improve the area-usage of the circuit board. It shouldbe noted that there is a spacing X1 between the signal line 122 and theground area 130, and there is a spacing X2 between the signal line 124and the ground area 130. For example, the spacing X1 is equivalent tothe spacing X2 (i.e., the first spacing). In addition, signal lines 122and 124 have line widths W122 and W124 respectively. The resistancevalue of the first transmission line 120 is related to the first spacingand line widths W122 and W124 of transmission lines 122 and 124. Forexample, when the value of the line widths W122 and W124 is fixed, theresistance value of the first transmission line 120 increases as thefirst spacing increases. When the value of the first spacing is fixed,the resistance value of the first transmission line 120 decreases as thevalue of the line width W122 and W124 increases.

Specifically, the first transmission line 120 including the signal lines122, 124 and the ground area 130 is a coplanar waveguide to guide andconvert the up-and-down directional electrical field of the firsttransmission line 120 into a left-and-right directional planarelectrical field. Compared with other well-known transmission lines,less of an up-and-down directional electrical field is generated by thefirst transmission line 120 of the coplanar waveguide. Therefore, theinterference caused by the wiring and grooving of other transmissionlines (such as the second transmission line 162) could be reduced. Whenthe electrical field of the radio signal passes through the wiring andgrooving of other transmission lines, the effect of the non-continuouselectrical field could be greatly decreased.

In one embodiment, the first transmission line 120 further includes thesingle-line area 126 (first single-line area) and the single-line area128 (second single-line area). The single-line area 126 connects thefirst terminal of the transmission lines 122 and 124, and thesingle-line area 128 connects the second terminal of the transmissionlines 122 and 124. The second terminal is relative to the firstterminal, and the second transmission line 162 does not interleave withthe single-line areas 126 and 128. It should be noted that the lengthL130 of the signal lines 122, 124 and the ground area 130 is larger thanor equal to the width W160 of the slot 160. As such, the firsttransmission line 120 includes the single-line areas 126 and 128 and thedouble-line area composed by the signal lines 122 and 124. The secondtransmission line 162 crosses and passes through the double-line areacomposed by the signal lines 122, 124 and the ground area 130 to reducethe signal-radiating effect. The length L130 of the double-line area islarger than or equal to the width W160 of the slot 160. In anotherembodiment, the length L130 of the double-line area could be defined asthe distance between the two via holes 130V of the ground area 130, butthe invention is not limited thereto.

The first transmission line 120 includes the single-line regions 126,128 and the double-line region which is composed of the signal lines122, 124 and the ground area 130. In order to match resistance to reducethe loss for transmitting signals, the spacing X1, X2 and the linewidths W122, W124 could be adjusted to obtain ideal resistance valuesfor the signal lines 122 and 124. In one embodiment, the resistancevalue of the single-line 126 is equal to the equivalent resistance valueof the signal lines 122 and 124, and the equivalent resistance value ofthe signal lines 122 and 124 are equal to the resistance value of thesingle-line area 128. For example, the resistance value of thesingle-line areas 126 and 128 are 50 ohm, and the resistance value ofthe signal lines 122 and 124 are 100 ohm. The equivalent resistancevalue of connecting the two signal lines 124 and 124 in parallel is also50 ohm, which is equal to the resistance value of the single-line areas126 and 128. Therefore, when the first transmission line 126 transmitsradio signals, the loss for transmitting radio signals could be reduceddue to the match of resistance. For example, when utilizing thetransmission line structure 10 of the present invention in the frequencyband of 20.6 GHz, the insertion loss of the signal is about −0.6 dB. Theinsertion loss of signals for those utilizing traditional back-boardwiring is about −1.9 dB. Therefore, because the resistance of the firsttransmission line 126 is matched to provide less insertion loss, theaccuracy and reliability of transmitting signals could be improved.

In the embodiment as shown in FIG. 1A, the transmission line structure10 further includes the ground areas 132 (the second ground area) and134 (third ground area) which are arranged on the first layer 100A. Theground areas 132 and 134 respectively have at least one via hole 132Vand 134V each for electrically connecting the ground area 136 on thesecond layer 100B. The signal line 122 is arranged between the twoground areas 130 and 132, and the signal line 124 is arranged betweenthe two ground areas 130 and 134. There is a spacing X3 (second spacing)between the signal line 122 and the ground area 132 and a spacing X4(third spacing) between the signal line 124 and the ground area 134. Forexample, the values of the spacing X1, X2, X3 and X4 are the same. Inother words, the first spacing is equal to the second spacing and thethird spacing. In another embodiment, the values of the spacing X3 andX4 are different. The second spacing is different from the thirdspacing. In addition, the resistance value of the first transmissionline 120 is related to the spacing X1, X2, X3 and X4, and is related tothe line widths W122 and W124 of the signal lines 122 and 124. Forexample, when the values of the line widths W122 and W124 are fixed, theresistance values of the signal lines 122 and 124 become largercorresponding to the increasing value of the spacing X1, X2, X3 and X4.When the value of the spacing X1, X2, X3 and X4 is fixed, the resistancevalue of the signal lines 122 and 124 becomes smaller corresponding tothe increasing value of the line widths W122 and W124. The spacing X1,X2, X3 and X4 and the line widths W122, W124 could be adjusted to obtainideal resistance value of the signal lines 122 and 124.

It should be noted that in one embodiment, the width W310 of the groundarea 310 is larger than or equal to three times the line widths W122 andW124 of the signal lines 122 and 124. The width W132 of the region wherethe ground area 132 is adjacent to the signal line 122 is larger than orequal to three times the line width W122 of the signal line 122. Thewidth W134 of the region where the ground area 134 is adjacent to thesignal line 124 is larger than or equal to three times the line widthW124 of the signal line 124. In other words, the present invention doesnot limit the width of the portion of the ground area 132 which is notadjacent to the signal line 122, and does not limit the width of theportion of the ground area 134 which is not adjacent to the signal line124. The above portions of the ground areas 132 and 134 which are notadjacent to the signal lines 122 and 124 could be any shape or sizeaccording to the circuit design. It should be noted that regarding thesignal line 122 or 124, the widths of the ground areas which areadjacent to the left side and the right side are larger than or equal tothree times the line width of the signal line 122 or 124. Therefore,when the signal line 122 or 124 transmits radio signals, itsleft-and-right directional electrical field could be blocked by theground area on its left side and right side whose width is more thanthree times. As such, the up-and-down directional electrical field ofthe signal line 122 or 124 could be reduced further, and theinterference which results from slot or wiring between the firsttransmission line 120 and the second transmission line 162 could beimproved. For example, when utilizing the transmission line structure 10of the present invention in the radio frequency band of 20.6 GHz, theminimum isolation of the signal is about −20.3 dB. The minimum isolationof signals for those utilizing traditional back-board wiring is about−10.2 dB. Therefore, since the transmission line structure 10 convertsthe electrical field into horizontal directional electrical field, abetter isolation could be provided to isolate the interference caused byother transmission lines which are arranged in up-and-down directions.

FIG. 2 is another top view of a transmission line structure 10 accordingto an embodiment of the invention. The transmission line structure 10includes the first transmission line 120 and the second transmissionline 162. The first transmission line 120 is arranged on the first layer100A of a circuit board, and the second transmission line 162 isarranged on the second layer 100B of the circuit board (not shown). Thesecond transmission line 162 does not contact the first transmissionline 120 to avoid causing a short-circuit. It should be noted that thefirst transmission line 120 is a coplanar waveguide. As shown in FIG. 2,the first transmission line 120 includes at least three signal lines122, 123 and 124, and at least two ground areas 130 and 131. The secondtransmission line 162 is interleaved with at least three signal lines122, 123, 124 and at least two ground areas 130 and 131. In oneembodiment, each of the ground areas 130 and 131 is arranged betweenevery two adjacent signal lines of the signal lines 122, 123 and 124.For example, the ground area 130 is arranged between the signal lines122 and 123, and the ground area 131 is arranged between the signallines 123 and 124. In addition, the width of each of the ground areas130 and 131 is larger than or equal to three times the line width ofeach of the signal lines 122, 123 and 124. In other words, the widthsW130 and W131 of the ground areas 130 and 131 are larger than or equalto three times the line widths W122, W123 and W124 of the signal lines122, 123 and 124.

In addition, as shown in FIG. 2, the transmission line structure 10further includes the ground area (second ground area) and the groundarea (third ground area) arranged on the first layer 100A. The groundareas 132 and 134 are arranged on the left side and the right side ofthe first transmission line 120 respectively. The spacing between theground area 132, the signal line 122, the ground area 130, the signalline 123, the ground area 131, the signal line 124 and the ground area134 are X5, X2, X1, X3, X4 and X6. In one embodiment, the width W132 ofthe portion of the ground area 132 which is adjacent to at least threesignal lines 122, 123 and 124 is larger than or equal to three times theline width W122, W123, W124 of the signal lines 122, 123 and 124. Thewidth W134 of the portion of the ground area 134 which is adjacent to atleast three signal lines 122, 123 and 124 is larger than or equal tothree times the line width W122, W123, W124 of the at least three signallines 122, 123 and 124. In another embodiment, the first transmissionline 120 vertically interleaves with the second transmission line 162,and the length L130 of each of the at least three signal lines 122, 123and 124 is larger than or equal to the width W160 of the slot 160. Thelength L130 of each of the at least two ground areas 130 and 131 islarger than or equal to the width W160 of the second transmission line.The length L130 could also be defined as the distance between the twovia holes 130V of the ground area 130, and the present invention is notlimited thereto.

In the embodiment of FIG. 2, the first transmission line 120 is acoplanar waveguide, and the line widths W122, W123, W124 of the signallines 122, 123, 124 are less than the width of the ground area which ison its left side and right side. Therefore, the up-and-down directionalelectrical field of the first transmission line 120 could be convertedinto a left-and-right directional electrical field. Since theup-and-down directional electrical field of the first transmission line120 is greatly reduced, the high-frequency coupling effect andinterference between the first transmission line 120 and the secondtransmission line 162 could also be greatly reduced. The amount ofsignal lines 122, 123, 124 and the ground areas 130, 131, 132 and 134 isfor illustration, not for limiting the present invention. Within thescope of the present invention, users can adjust the spacing, linewidth, and amount of transmission lines and ground areas according toneed for the circuit design to achieve resistance-matching and reducethe loss for transmitting signals. Therefore, the accuracy andreliability of transmitting signals can be improved.

Use of ordinal terms such as “first”, “second”, “third”, etc., in theclaims to modify a claim element does not by itself connote anypriority, precedence, or order of one claim element over another or thetemporal order in which acts of a method are performed, but are usedmerely as labels to distinguish one claim element having a certain namefrom another element having the same name (but for use of the ordinalterm) to distinguish the claim elements. While the invention has beendescribed by way of example and in terms of the preferred embodiments,it is to be understood that the invention is not limited to thedisclosed embodiments. On the contrary, it is intended to cover variousmodifications and similar arrangements (as would be apparent to thoseskilled in the art). Therefore, the scope of the appended claims shouldbe accorded the broadest interpretation so as to encompass all suchmodifications and similar arrangements.

What is claimed is:
 1. A transmission line structure for transmittingradio signals, comprising: a first transmission line, arranged on afirst layer of a circuit board, wherein the first transmission linecomprises a first signal line and a second signal line, a first terminalof the first signal line connects to a first terminal of the secondsignal line, and a second terminal of the first signal line connects toa second terminal of the second signal line, and the second terminal ofthe first signal line and the second signal line is relative to thefirst terminal of the first signal line and the second signal line; afirst ground conductor, arranged on the first layer and between thefirst signal line and the second signal line, wherein the first signalline and the second signal lines do not contact the first ground area;and a second transmission line, arranged on a second layer of thecircuit board, wherein the second layer is different from the firstlayer, the second transmission line does not contact the firsttransmission line, and the second transmission line overlaps with thefirst signal line, the second signal line and the first ground area. 2.The transmission line structure as claimed in claim 1, wherein the firstsignal line and the first ground conductor are spaced by a firstdistance, and the second signal line and the first ground are spaced bythe first distance.
 3. The transmission line structure as claimed inclaim 2, wherein the transmission line structure further comprises asecond ground conductor and a third ground area arranged on the firstlayer, and the first signal line is arranged between the first groundlayer and the second ground layer, the second signal line is arrangedbetween the first ground layer and the third ground layer, the firstsignal line and the second ground conductor are spaced by a seconddistance, and the second signal line and the third ground conductor arespaced by a third distance.
 4. The transmission line structure asclaimed in claim 3, wherein a width of the first ground conductor islarger than or equal to three times the line widths of the first signalline and the second signal line.
 5. The transmission line structure asclaimed in claim 4, wherein a width of a portion of the second groundconductor which is adjacent to the first signal line is larger than orequal to three times the line width of the first signal line, and awidth of a portion of the third ground conductor which is adjacent tothe second signal line is larger than or equal to three times the linewidth of the second signal line.
 6. The transmission line structure asclaimed in claim 3, wherein the first distance is equal to the seconddistance and the third distance.
 7. The transmission line structure asclaimed in claim 3, wherein the resistance value of the firsttransmission line is related to the first distance, the second spacing,the third distance, and line widths of the first signal line and thesecond signal line.
 8. The transmission line structure as claimed inclaim 2, wherein the resistance value of the first transmission line isrelated to the first distance and line widths of the first signal lineand the second signal line.
 9. The transmission line structure asclaimed in claim 1, wherein the first transmission line furthercomprises a third signal line and a fourth ground conductor, the fourthground conductor is arranged between the second signal line and thethird signal line, the second transmission line overlaps with the firstsignal line, the second signal line, the third signal line, the firstground conductor, and the fourth ground conductor, wherein the firstterminal of the third signal line connects to the first terminal of thefirst signal line and the second signal line, the second terminal of thethird signal line connects to the second terminal of the first signalline and the second signal line, and the second terminal is relative tothe first terminal.
 10. The transmission line structure as claimed inclaim 9, wherein the transmission line structure further comprises asecond ground conductor and a third ground conductor arranged on thefirst layer, and the second ground conductor and the third groundconductor are arranged on two sides of the first transmission line. 11.The transmission line structure as claimed in claim 10, wherein a widthof a portion of the second ground conductor which is adjacent to thefirst transmission line is larger than or equal to three times the linewidth of each of the first signal line, the second signal line and thethird signal line, and a width of a portion of the third groundconductor which is adjacent to the first transmission line is largerthan or equal to three times the line width of each of the first signalline, the second signal line and the third signal line.
 12. Thetransmission line structure as claimed in claim 9, wherein a width ofeach of the first ground conductor and the fourth ground area is largerthan or equal to three times the line width of each of the first signalline, the second signal line, and the third signal line.
 13. Thetransmission line structure as claimed in claim 9, wherein the firstsignal line, the second signal line, the third signal line, the firstground conductor and the fourth ground conductor are vertically offsetto the second transmission line, and a length of each of the firstsignal line, the second signal line and the third signal line is largerthan or equal to a width of the second transmission line, and a lengthof each of the first ground conductor and the fourth ground conductor islarger than or equal to a width of the second transmission line.
 14. Thetransmission line structure as claimed in claim 9, wherein the firsttransmission line further comprises a first single-line area and asecond single-line area, the first single-line area connects to thefirst terminal of the first signal line, the second signal line and thethird signal line, the second single-line area connects to the secondterminal of the first signal line, the second signal line and the thirdsignal line, and the second transmission line does not overlap with thefirst single-line area and the second single-line area.
 15. Thetransmission line structure as claimed in claim 1, wherein the firstsignal line, the second signal line and the first ground conductor arevertically offset from the second transmission line.
 16. Thetransmission line structure as claimed in claim 15, wherein a length ofthe first signal line, the second signal line and the first groundconductor are larger than or equal to a length of the secondtransmission line.
 17. The transmission line structure as claimed inclaim 1, wherein the first transmission line further comprises a firstsingle-line area and a second single-line area, the first single-linearea connects to the first terminal of the first signal line and thefirst terminal of the second signal line, the second single-line areaconnects to the second terminal of the first signal line and the secondterminal of the second signal line, and the second transmission linedoes not overlap with the first single-line area and the secondsingle-line area.
 18. The transmission line structure as claimed inclaim 17, wherein the resistance value of the first single-line area isequal to an equivalent resistance value of the first signal line and thesecond signal line, and the equivalent resistance value of the firstsignal line and the second signal line is equal to resistance value ofthe second single-line area.
 19. The transmission line structure asclaimed in claim 1, wherein the first transmission line is a coplanarwaveguide.